Voltage sources based, for example, on the Seebeck effect generate electrical voltages which are formed in dependence on a temperature. The voltages generated thereby are very low and, due to the very low voltage values, can only be used in a very restricted way as a voltage source for operating other electrical circuits. The Seebeck effect describes that, if two solder joints between different materials having different temperatures are formed in a closed electrical conductor, an electrical current flows, the so-called thermocurrent. This thermocurrent can be measured for temperature differences of only 1 Kelvin and below. The resultant thermal voltage is dependent on the metals used, for example metal pairings. In principle, however, the thermal voltage of a single thermocouple is very low. To increase the voltage generated, it is a known procedure to operate thermocouples in a series circuit and thus to achieve higher output voltages. Since each individual one of the thermocouples has its own internal impedance, the series connection of the thermocouples also increases the total internal impedance disadvantageously. A higher output voltage is thus gained with the disadvantage of lower efficiency. This disadvantage can be transferred not only to thermocouples but also applies to other voltage sources which supply low or very low voltages. Since each voltage source has a certain internal impedance, connecting voltage sources in series also, of necessity, produces an addition of the internal impedances. Operating thermocouples in parallel, or constructing the thermocouples with a greater area, on the other hand, does not generate a higher voltage but a higher current and accordingly a higher thermocurrent. The parallel circuit advantageously improves the internal impedance since the internal impedance of the overall circuit is then advantageously reduced.
The disadvantageous factor is that known semiconductor circuit arrangements cannot be operated with the low voltages which can then be achieved. Semiconductor circuits need an electrical voltage which exceeds a threshold of at least 0.3 V. Above this value, semiconductor-based voltage converter circuits can also be used.